Annealing effects on the crystal structure of GaInNAs quantum wells with large In and N content grown by molecular beam epitaxy

Abstract

The impact of rapid thermal annealing on the optical emission of GaInNAs/GaAs quantum wells (QWs) grown by molecular beam epitaxy with high In and N content is shown to be highly dependent on the crystal structure of the QWs, as determined by transmission electron microscopy. Due to the presence of higher concentrations of nonradiative recombination centers, the annealing temperature required to obtain maximum photoluminescence emission is higher for the QW with strong structural modulation of the upper interface [at the onset of three-dimensional (3D) growth], intermediate for the two-dimensional (2D) grown QW with compositional fluctuations, and lower for the homogeneous 2D grown QW. Moreover, the transition from homogeneous 2D growth, to 2D growth with compositional fluctuations, and finally 3D growth, leads to progressively deeper carrier localization states below the conduction-band edge. Increasing annealing temperatures gradually shifts the localization states closer to the conduction-band edge, predominantly when compositional fluctuations are present. These results suggest a link between the formation of carrier localization centers and the presence of alloy fluctuations along the QW.

SPSLs and Dilute-Nitride Optoelectronic Devices

“…In some cases, PL spectra measured as T is increased from ∼10 to 300 K display two peaks, one of which diminishes with increasing T (characteristic of LE emission) and the other of which increases with T (characteristic of free exciton (FE) emission) Buyanova et al (2002); Mair et al (2000); Shirakata et al (2002). In addition, the S-shaped temperature dependence of the peak emission wavelength for GaNAs samples also suggest that localised excitons dominate recombination at low T in dilute nitrides Hierro et al (2003); Mazzucato et al (2003); Pomarico et al (2002). To date, the reasons offered for localisation at low T relate to compositional fluctuations within the lattice Buyanova et al (2003) (2002); Pan et al (2000).…”

“…Unfortunately, a full understanding of the fundamental nature and behaviour of nitride alloys, especially during the annealing treatments that are required for optimum performance, continues to elude researchers. Certain trends have been identified qualitatively, such as that optimum anneal conditions depend on composition, and more specifically on (2D/3D) growth mode Hierro et al (2003), on nitrogen content Francoeur et al (1998); Loke et al (2002), and on indium content for GaInNAs Kageyama et al (1999), but 'optimum' annealing treatments continue to vary widely, according to growth method, growth conditions, structure and composition. We believe that SPSL structures have an important role to play in such studies.…”

“…If the degradation of PL intensity is related to defect density, then performance enhancement through the annealing-out of defects is certainly limited. Additionally, the model suggested by Grenouillet et al Grenouillet et al (2002) to explain optical performance based on composition fluctuations has been demonstrated both theoretically and experimentally Grenouillet et al (2002); Pan et al (2000) to result in a limit beyond which improvement is negligible, although some papers have shown that 'extreme' annealing can also cause samples to degrade after passing through an 'optimal' state see Hierro Hierro et al (2003), Gupta et al Gupta et al (2003) and Xin et al Xin et al (2000). The presence of hydrogen (which pacifies optically-active centers) can also confuse matters, since its incorporation during 'gas-source' and 'metal-organic' growth and subsequent out-diffusion during annealing can augment perceived improvements in optical efficiency Klar et al (2003);v H G Baldassarri et al (2001).…”

Optical transitions in GaNAs quantum wells with variable nitrogen content embedded in AlGaAs

“…3,11 From previous experiments the dependence of GaN x As 1−x band gap energy and the behavior of the confined ground state energy in GaNAs/GaAs QWs have been studied. Deeper N-induced localized energy states lead to a characteristic S-shaped temperature dependence of PL emission energy of Ga(In)NAs/GaAs QWs, 3,4,10,[12][13][14][15][16][17] however reported dependencies vary widely depending on growth conditions. a Author to whom correspondence should be addressed; electronic mail: ELBORG.Martin@nims.go.jp Due to its extremely large bowing factor, the incorporation of N into GaAs enables the tuning of the band gap from 1.42 -1.0 eV for N concentrations of 0 -5%, 1 which makes the material useful for application in optical detectors, sub-cells in multi-junction solar cells, 18 and long-wavelength emitters.…”

“…4 To understand these complex properties, several studies have been performed on bulk GaNAs or GaNAs/GaAs quantum wells (QWs) employing absorption techniques like photoreflectance [5][6][7] or surface photovoltage spectroscopy, 8 as well as emission techniques such as photoluminescence (PL) measurement. 9,10 Only few studies have combined emission and absorption techniques. 3,11 From previous experiments the dependence of GaN x As 1−x band gap energy and the behavior of the confined ground state energy in GaNAs/GaAs QWs have been studied.…”